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4.1 Properties of Minerals


Vocabulary


inorganic- when a mineral cannot rise from the materials that were once part of a living thing
crystal- when the repeating pattern of a mineral's particles forms a solid
element- a substance made of only one kind of atom
compound- when two or more elements are combined
Mohs hardness scale- it ranks ten minerals from softest to hardest
streak- the color of the mineral's powder
luster- a term used to describe how a certain mineral reflects light from its surface
cleavage- a mineral that splits easily along flat surfaces has this property
fracture- describes how a mineral looks when it breaks apart in an odd way
fluorescence- minerals that glow under ultra violet light have this property

Outline


What is a Mineral?

  • any mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition
  • naturally occurring
    • substances found in Earth's crust that are manufactured by people, are not considered minerals
  • inorganic
    • a mineral must also be inorganic
  • solid
    • minerals are always solid
  • crystal structure
    • particles in a mineral line up in a pattern that keeps going on and on
      • this process forms crystals
  • definite crystal composition
    • all minerals have a definite chemical composition
    • almost all minerals on Earth are compound
    • almost all pure elements on Earth are metals

Identifying Minerals

  • Each mineral has their own specific properties that can be used, if needed, to identify it
  • hardness
    • Mohs Hardness Scale
      • Friedrich Mohs invented it
      • it can identify a mineral's hardness
    • a mineral can scratch any other mineral that is softer than itself
  • color
    • minerals can occur in a variety of colors
  • streak
    • a streak of a mineral is the color of its powder
    • a mineral's streak can be different from its appearance color
  • luster
    • luster is the term used to describe how a certain mineral reflects light from its surface
  • density
    • you can measure and compare minerals by comparing their density
  • crystal systems
    • crystals that grow in an open space usually grow almost perfectly
    • crystals that don't grow in an open space are often incompletely formed
  • cleavage and fracture
    • a mineral that splits easily along flat surfaces has the property named cleavage
    • a fracture describes how a mineral looks when it breaks apart in an irregular way
  • special properties
    • some minerals glow under ultraviolet light, so they have a property called fluorescence
    • some minerals are magnetic
    • some minerals are radioactive
    • some minerals have electrical properties
    • some minerals react chemically to acid

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